1. Field of the Invention
The present invention relates to a motor-driven engine starter that has a pinion to be engaged with a ring gear of an engine.
2. Description of the Related Art
JP-Y2-55-45900 discloses a starter that has a starting motor, an output shaft, a spline tube, a pinion and an electromagnetic switch that has a drive spring. The output shaft and the spline tube are connected by a helical spline connection so that the electromagnetic switch pushes the pinion via a lever to engage a ring gear of an engine when the electromagnetic switch operates.
However, there is a considerable probability, such as 40%-60%, that the pinion cannot completely engage the ring gear in such a starter. In order to provide the complete engagement of the pinion with the ring gear, the starting motor forcibly rotates the pinion under the spring force of the drive spring. In that case, the pinion and the ring gear are subject to a considerable shock and may wear or crack.
Although the pinion is rotated a little by the helical spline connection under a combined spring force of the pinion spring and the drive springs before the starting motor operates, the pinion spring and the drive spring are not arranged to allow the pinion to rotate a suitable angle to increase the probability of the complete engagement. In other words, the pinion spring is not compressed to provide a suitable stroke for the pinion to rotate about the output shaft by such a suitable angle.